1. Field of the Invention
This invention relates to gravity flow timing devices such as the conventional hourglass type sand timer and, in particular, to such a timer designed for economical manufacture and to enable quick resetting when in use.
2. Description of the Prior Art
Timers which depend on the metering of particulate matter through a flow restricting orifice have long existed. Until very recently, those used as game timers have been made of glass as distinguished from plastic, since the fine particular matter used in glass timers had a tendency to cling to the transparent plastics available, thus rendering the timers inaccurate. But glass timers have no provision for being quickly reset when only part of the sand has drained from the upper to the lower chamber. Additionally, the constraints involved in using glass to manufacture such objects have made it infeasible to modify them so as to provide a means for rapidly resetting them.
The fact that glass timers cannot be quickly reset greatly limits their usefulness as game timers. Very often game players using glass timers complete their turns before all the sand has drained from the upper chamber (metering receptacle) into the lower chamber to signify lapse of a time interval. Commencement of another time interval requires delaying the game either until all sand has finished draining from the upper chamber or has been returned to the upper chamber by inversion of the timer, which means, in either case, waiting until the sand has all slowly passed through the small metering opening between the two chambers. Accordingly, to permit quick reset, it is one of the objects of my invention to provide a gravity flow timer having means for free flow return to the metering receptacle of the particulate matter which has drained from it. I have discovered that it is practicable for gravity flow timers to be injection molded from a substantially transparent plastic. Accordingly, since plastics can now replace glass in such timers, it is another object of the invention to provide a variety of practicable configurations to replace the hourglass shape. A still further object is to provide injection moldable configurations that can be mass produced to provide a gravity flow timer adapted for quick resettability.
Gravity flow timers exist which aim to provide for quick resettability. Some of the earlier ones patents, however, required the use of moving parts, as in U.S. Pat. Nos. 2,144,857 and 3,125,849. In addition to any production disadvantages they might have, such timers would tend to be less reliable than gravity flow timers with no moving parts. It is therefore another object of my invention to provide a quickly resettable timer having no moving parts other than the particulate matter it contains, and which may be economically manufactured.
Some one-piece gravity flow timers designed for quick resettability can only be properly reset by rotating the timer carefully in a particular way. This is true of the inventions disclosed in U.S. Pat. Nos. 4,813,030, 4,117,666 and 4,408,894. Accordingly, another object of my invention is the provision of a quickly resettable timer that may be reset simply by inversion and then return to upright position with no special care required in doing so.
There is a timer disclosed in U.S. Pat. No. 4,648,721 which can be easily reset and which has no moving parts, but which requires the separate manufacture and assembly of five parts and which discloses no method for fastening two key parts inside a third part, a problematic operation in mass production manufacture. It is therefore another object of my invention to provide an injection molded timer device that eliminates the necessity of time consuming and therefore costly assembly.
It is therefore a broad object of my invention to provide a timer that will meet the following criteria: easy to mold; simple, i.e. consists of but one piece; constructed from a minimal amount of plastic; reliable; and quickly and easily resettable, no matter how it is inverted or returned to upright in the resetting process.